Upgraded Giant Metrewave Radio Telescope timing of NGC 1851A: a possible millisecond pulsar-neutron star system. (arXiv:1909.06163v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+Ridolfi_A/0/1/0/all/0/1">Alessandro Ridolfi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Freire_P/0/1/0/all/0/1">Paulo C. C. Freire</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gupta_Y/0/1/0/all/0/1">Yashwant Gupta</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ransom_S/0/1/0/all/0/1">Scott M. Ransom</a>
(abridged) In this work we present the results of one year of upgraded Giant
Metrewave Radio Telescope timing measurements of PSR~J0514$-$4002A, a 4.99-ms
pulsar in a 18.8-day, eccentric ($e , =, 0.89$) orbit with a massive
companion located in the globular cluster NGC~1851. Combining these data with
earlier Green Bank Telescope data, we greatly improve the precision of the rate
of advance of periastron, $dot{omega} , = , 0.0129592(16), deg , rm
yr^{-1}$ which, assuming the validity of general relativity, results in a much
refined measurement of the total mass of the binary, $M_{rm tot} , = ,
2.4730(6) , M_{odot}$. Additionally, we measure the Einstein delay parameter,
$gamma,, = , 0.0216(9) , rm s$. Furthermore, we measure the proper motion
of the system ($mu_{alpha} , = , 5.19(22)$ and $mu_{delta} =
-0.56(25)rm~mas ~ yr^{-1}$), which is not only important for analyzing its
motion in the cluster, but is also essential for a proper interpretation of
$gamma$, given the latter parameter’s correlation with the variation of the
projected semi-major axis. The measurements of $gamma$ and the proper motion
enable a separation of the system component masses: we obtain a pulsar mass of
$M_{p} , = , 1.25^{+0.05}_{-0.06} , M_{odot}$ and a companion mass of
$M_{c} , = , 1.22^{+0.06}_{-0.05} , M_{odot}$. This raises the possibility
that the companion is also a neutron star. Searches for radio pulsations from
the companion have thus far been unsuccessful, hence we cannot confirm the
latter hypothesis. The low mass of this millisecond pulsar – one of the lowest
ever measured for such objects – clearly indicates that the recycling process
can be achieved with a relatively small amount of mass transfer.
(abridged) In this work we present the results of one year of upgraded Giant
Metrewave Radio Telescope timing measurements of PSR~J0514$-$4002A, a 4.99-ms
pulsar in a 18.8-day, eccentric ($e , =, 0.89$) orbit with a massive
companion located in the globular cluster NGC~1851. Combining these data with
earlier Green Bank Telescope data, we greatly improve the precision of the rate
of advance of periastron, $dot{omega} , = , 0.0129592(16), deg , rm
yr^{-1}$ which, assuming the validity of general relativity, results in a much
refined measurement of the total mass of the binary, $M_{rm tot} , = ,
2.4730(6) , M_{odot}$. Additionally, we measure the Einstein delay parameter,
$gamma,, = , 0.0216(9) , rm s$. Furthermore, we measure the proper motion
of the system ($mu_{alpha} , = , 5.19(22)$ and $mu_{delta} =
-0.56(25)rm~mas ~ yr^{-1}$), which is not only important for analyzing its
motion in the cluster, but is also essential for a proper interpretation of
$gamma$, given the latter parameter’s correlation with the variation of the
projected semi-major axis. The measurements of $gamma$ and the proper motion
enable a separation of the system component masses: we obtain a pulsar mass of
$M_{p} , = , 1.25^{+0.05}_{-0.06} , M_{odot}$ and a companion mass of
$M_{c} , = , 1.22^{+0.06}_{-0.05} , M_{odot}$. This raises the possibility
that the companion is also a neutron star. Searches for radio pulsations from
the companion have thus far been unsuccessful, hence we cannot confirm the
latter hypothesis. The low mass of this millisecond pulsar – one of the lowest
ever measured for such objects – clearly indicates that the recycling process
can be achieved with a relatively small amount of mass transfer.
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